Letters

Authors' reply

The idea of notional courses is widely used in retrospective research.¹ The number of cases of C difficile diarrhoea relating to each antibiotic is the basis for the calculation of the risk ratios. We also clearly stated in our paper that one in five patients who received cefotaxime developed C difficile diarrhoea. The diagnostic test for the toxin has been well validated.² We are surprised by the belief that cefotaxime has limited effect on normal gut flora, as even a study in healthy volunteers has shown that, after a single intravenous injection of 1.5 g cefotaxime, two out of six excreted C difficile in their stools and one developed diarrhoea.³ Antibiotic treatment has been identified as the most important risk factor for C difficile diarrhoea, especially in elderly people.⁴ The incidence of C difficile diarrhoea of 1.2% quoted by Rothschild and colleagues in patients treated with cefotaxime was derived from studies of younger patients, in whom the risk is greatly reduced. Our paper highlights the problems that arise when these data are extrapolated to very old people. The median age of our patients was nearly 84. We trust that expert panels will in future take notice of the issues raised in our paper.

M Lesna and D M Parham produce data derived from geriatric patients of similar age to ours. Although the mortality in our sample was lower than that in theirs (42% v 64%), we agree with their observation that C difficile diarrhoea is accompanied by increased morbidity. Their conclusion is in keeping with the gist of our paper--that a further increase in hospital acquired C difficile colitis may be predicted if widespread use of broad spectrum antibiotics continues unabated.

Consultant Senior registrar Care of the Elderly Unit, Department of Medicine, Royal Postgraduate Medical School, Hammersmith Hospital, London W12 0NN

Professor Department of Infectious Diseases, Royal Postgraduate Medical School

M Impallomeni, J Starr, T Rogers 

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